Abstract: The effects on the arsenic spectrophotometric absorption signal and hydride generation of the reaction medium (HCl: 0-0.05 M), reducing agent (NaBH(4): 0.2-1% stabilised in NaOH: 0.2-1%), prereducing agent (L-cysteine: 0-2%) and contact time between L-cysteine and arsenic (III) and arsenic (V) solutions were investigated using FIA-HG-QFAAS. The speciation procedure involved three steps: (i) arsenic (III) determination immediately after the sample was mixed with L-cysteine; (ii) total arsenic determination after a 10 min-contact time between sample and L-cysteine by boiling in water bath at 90 +/- 5 degrees C and (iii) arsenic (V) determination as difference between total arsenic and arsenic (III). Under optimised conditions to generate arsine from arsenic (III) (0.01 M HCl, 0.2% L-cysteine, 0.6% NaBH(4) in 0.5% NaOH), the arsenic speciation was possible with good recovery (98-105%) for arsenic (III), arsenic (V) and total arsenic. A rigorous pH control at 2.00 +/- 0.01 prior to arsine generation was necessary. The detection limit based on 3 sigma criteria and parameters of calibration curve was 0.1 ng mL(-1) arsenic. The simple and inexpensive optimised method is used for the determination of leachable inorganic arsenic species within a distribution study of arsenic in the Baia-Mare area, Romania, which is the subject of another paper.